The invention relates generally to communication systems and more specifically concerns a technique for increasing the data capacity of communication systems.
It is reasonable to expect that future communication systems will be allegated only a very limited spectrum in desirable frequency bands, while bandwidths of signals will be increasing. Several approaches, such as more efficient analog-to-digital conversion, more efficient modulation techniques, and dual polarization can be used to increase the data capacity of the available spectrums. This invention relates to the dual polarization technique for increasing the data capacity.
With the technique of dual polarization, different channels are established for each of two orthogonal polarizations transmitted. Obviously, if the two polarizations can be separated sufficiently, the effective data capacity for a given bandwidth is doubled. However, in a typical communication system, the received polarizations are rarely completely separated due to cross polarization crosstalk from various sources such as rain, nonperfect antennas, and ionospheric propagation. The presence of crosstalk will cause some degradation of the channel capacity of a communication system and thus, it may have to be reduced to a lower level for full potential of dual polarization to be realized. This reduction can be done with a cross polarization correction network.
In order to achieve a polarization correction network, in the face of varying cross polarization (due to such factors as varying rain), the correction network should be automatic or adaptive so as to track the varying cross polarization. The past dual polarization correction networks require a general search optimization algorithm and do not have a direct analog control.
It is therefore the primary purpose of this invention to provide a dual polarization correction network that is automatic or adaptive so as to track the varying cross polarization.
It is another object of this invention to provide a direct analog controlled dual polarization correction network.
Other objects and advantages of this invention will become apparent hereinafter in the specifications and drawings.